From The Collaborative International Dictionary of English v.0.48 :
Barbed \Barbed\, a.
Furnished with a barb or barbs; as, a barbed arrow; barbed
wire.
[1913 Webster]
Barbed wire, a wire, or a strand of twisted wires, armed
with barbs or sharp points. It is used for fences.
[1913 Webster]
From WordNet (r) 3.0 (2006) :
barbed wire
n 1: strong wire with barbs at regular intervals used to prevent
passage [syn: barbed wire, barbwire]